A hybrid electric vehicle powertrain includes an engine and an electric motor, wherein torque (or power) produced by the engine and/or the motor can be transferred through a transmission to the vehicle drive wheels to propel the vehicle. A traction battery supplies energy to the motor. In certain powertrains, the engine is connectable to the motor by a disconnect clutch and the motor is connected to the transmission. The motor may be connected to the transmission via a torque converter. The engine, the disconnect clutch, the motor, the torque converter, and the transmission are connected sequentially in series.
Hybrid vehicle controls rely on an accurate value of the power loss of the motor. For instance, the calculation of motor torque to wheel, battery power limits and plausible violations, charging power to battery from energy management algorithm, maximum allowable regenerative brake limit, and other control strategies rely on an accurate estimation of the motor power loss.
Motor power loss is generally a function of motor speed, motor torque, and traction battery voltage supplied to the motor. Estimates of motor power losses for given combinations of motor speed and motor torque at given battery voltages can be predefined. Such predefined estimates may be generated by testing the motor (or, more particularly, for example, the finished motor prototype) on a dynamometer. The predefined estimates are stored in a map. Vehicle controls subsequently access the map to obtain an estimation of the motor power loss at a given time during operation of the vehicle and use the estimation in their control routines.
Variability in the motor during manufacturing or degradation of motor efficiency with time, temperature, and/or duty cycle can result in varied motor power losses. The predefined motor power loss map cannot capture such variability and changes.